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Smith & Wesson Model 642

• moderate
• Shop tier 2
• medium confidence
• Revolver
• revolver
• double action
• sideplate
• concealed carry
• double action only
• j frame

field strip ~3 min · reassembly ~4 min · detail strip ~45 min

Specifications

Model-specific safety

• A revolver is not cleared by opening the cylinder. Look through every chamber and count them.
• Revolver internals are gunsmith territory. Removing the sideplate to reach the lockwork is easy to do and very easy to do damage with. Unless you know what you are doing, stop at cylinder and yoke removal.
• Never pry the sideplate off. Loosen the screws and tap the grip frame with a non-marring mallet until the plate lifts free. Prying permanently marks a fitted surface.
• Smith & Wesson sideplate screws are not interchangeable. Keep them in order.
• Never close the cylinder by flicking the wrist. It springs the yoke and puts the revolver out of time.
• The hammer is fully enclosed by the frame on this model, so it is double-action-only and cannot be thumb-cocked. There is no hammer to check visually — the chamber check is the only check.

Under spring tension

• Rebound slide spring (sideplate removal — it launches)
• Mainspring
• Cylinder stop spring

Easily lost parts

Yoke retaining screw · Sideplate screws · Rebound slide and spring · Cylinder stop

Tools

Shop difficulty

Shop tier 2 Tier 2 — moderate among revolvers, for the full job: strip to the parts that get coated and put it back together working. J-frame Airweight: no hammer block (shrouded hammer) and fewer parts than a K-frame, but a stiff rebound slide spring on a steel stud pressed into an aluminum frame that is easy to damage, plus an uncaptured MIM hand spring. Moderate.

Parts: 57 numbered parts (stand-in: S&W Model 38 Bodyguard Airweight (alloy-frame J-frame .38, shrouded hammer) factory Parts Price Schedule, View # 1-57. Assembly lines (8-10, 20-26, 40-41, 45-47, 51-55) have no number of the), from Smith & Wesson Model 38 (Bodyguard Airweight) - factory Parts Price Schedule, View # 1-57 (scanned image; exploded view at SW38.jpg) — Smith & Wesson (factory sheet), scan hosted by CFN Parts cfnparts.com [10].

Bench time: about 35 min to strip, 55 min to rebuild (estimate). Estimated for an experienced tech: grips, sideplate, lockwork, crane/cylinder, thumbpiece/bolt. No hammer block and fixed sights, so no sight time; rebuild still dominated by the rebound spring and hand spring. TM figures for the K-frame M10 given as a cross-check only.

Small parts: 11 pins, 9 springs, 1 detents or plungers (counted by name in the same list, by view number: Pins 1 Barrel Pin, 6 Center Pin, 9 Extractor Pin, 25 Stirrup Pin, 26 Sear Pin, 30 Hand Pin, 33 Locking Bolt Pin, 41 Rebound Slide Pin, 48 Stock Pin, 5)

What comes off for coating

• Grips and sideplate: grips, sideplate screws (kept in their holes), sideplate (tapped free, never pried) — fitted hollow-ground screwdrivers, nylon mallet
• Lockwork: coil mainspring on its strut (captured with a pin/paper clip), rebound slide, rebound slide spring, shrouded hammer, trigger with hand and hand spring, cylinder stop and spring, internal-lock parts (if fitted) — rebound slide spring tool or small Phillips screwdriver, paper clip or pin for the mainspring strut
• Cylinder and crane: cylinder and crane, extractor rod and center pin springs if the cylinder is coated — padded vise
• Frame (aluminum alloy): thumbpiece nut and thumbpiece, bolt, bolt plunger and spring, locking bolt, spring and pin — pin punch

Special tools

• Rebound slide spring tool (Brownells S&W tool) or a Phillips screwdriver just larger than the spring ID — Compressing and re-seating the rebound slide spring over its stud
• Fitted hollow-ground (gunsmith) screwdrivers — Sideplate, strain, thumbpiece and stock screws without burring
• Nylon/brass or rawhide mallet — Tapping the frame to lift a tight sideplate
• Large clear plastic bag — Containing the rebound spring and small springs on removal

Known pain points

• The J-frame rebound slide spring is stiff and tends to take flight whichever tool is used. (both)
  Owners report: J frame sideplate removal — Smith & Wesson Forum smith-wessonforum.com [5] — “It can be a bit tricky either way, and that spring can always take flight and disappear if you are not careful, no matter what tool you use.”
• On the aluminum frame the rebound slide stud is a steel pin pressed into aluminum and can crack loose if forced while the spring is worked. (both)
  Source: Do-It-Yourself Smith & Wesson J-Frame Trigger Job: How-To — Shooting Times shootingtimes.com [6] — “If you’re doing a spring change on an aluminum frame, be extra careful to not put too much force on the rebound (trigger) slide stud. It is a steel pin pressed into an aluminum frame, and the joint is not as strong as a steel frame.”
• On MIM-trigger 442/642s the hand spring fits differently and is frustrating to refit without knowing the layout. (reassembly)
  Owners report: How does the hand spring fit on 442/642 — Smith & Wesson Forum smith-wessonforum.com [7] — “Fitting the hand spring turns out to be simple if you know how to approach it, and an exercise in frustration if you just monkey around with”
• Smith & Wesson tells owners not to go beyond the field strip; lockwork work is for a qualified gunsmith. (both)
  Source: Safety & Instruction Manual, Revolvers - Modern Style - J, K, L and N Frame (p/n 416560000, REV S&W_REVOLVER_112119), linked from smith-wesson.com revolver product pages — Smith & Wesson smith-wesson.canto.com [2] — “NEVER DISASSEMBLE YOUR FIREARM beyond the field stripping procedure outlined in this manual. Improper disassembly or reassembly of your firearm may be dangerous and can lead to serious injury or death.”

Fit or check on rebuild

• Timing / carry-up: each chamber must lock before the hammer falls, single and double action — The hand torsion spring must engage the hand; a hand pulled back too far loses spring tension and the cylinder will not index.
  Source: Change of a 686 rebound spring — Smith & Wesson Forum smith-wessonforum.com [8] — “make certain you still have spring tension on the hand (some people accidentally pull the hand back too far when removing or installing the trigger, causing the internal stud on the hand to slip past the spring inside the trigger).”
• Cylinder gap (barrel-cylinder) and end shake; crane alignment — The Army issues gauges for exactly these checks when the cylinder/yoke group is replaced.
• Firing-pin (hammer-nose) protrusion and hammer-block function — Same TM lists a firing-pin protrusion gauge; the hammer block must ride up on the rebound slide pin before the sideplate goes on.
  Source: Installing Smith & Wesson Spring Kit — Shooting Times shootingtimes.com [9] — “The hammer-block safety will be lying loose under it, so take care to note how it goes in. There is a small pin on the rebound slide where it rides.”
• Sideplate seats flush with no forcing; strain screw fully tightened — A sideplate that is not flush binds the grips and parts behind it; a backed-out strain screw gives light strikes (well-known S&W check).
• Trigger reset with the rebound spring fitted — The rebound slide spring is also the trigger return spring.
  Source: Installing Smith & Wesson Spring Kit — Shooting Times shootingtimes.com [9] — “The downside is that the rebound also serves as the trigger return spring”
• Rebound slide stud tight in the aluminum frame — The stud is pressed into aluminum and can loosen or crack during spring work.
  Source: Do-It-Yourself Smith & Wesson J-Frame Trigger Job: How-To — Shooting Times shootingtimes.com [6] — “If you’re doing a spring change on an aluminum frame, be extra careful to not put too much force on the rebound (trigger) slide stud. It is a steel pin pressed into an aluminum frame, and the joint is not as strong as a steel frame.”

This is Pew-Takedown's rating, not the manufacturer's. How tiers are rated. Forum reports are owners' experience, not specifications.

Manufacturer videos

Official videos from Smith & Wesson's own channels, linked rather than copied. Where a video and the steps on this page differ, follow the manufacturer's manual and video.

• How To Clean a Revolver | Smith & Wesson® Smith & Wesson cleaning, maintenance · 2026-02-23
  Covers: Revolvers in general (S&W's own generic guide; no model named in title/description)
• Unloading & Reloading Revolvers Smith & Wesson clearing, operation · 2021-07-13
  Covers: Revolvers in general (GUNSMARTS series, Jerry Miculek; no model named)

Procedures

Patent drawings

not under copyright

Drawings from US patents on this design. A patent shows the invention as the inventor filed it; the firearm that shipped can differ in detail, and later production often does. Use them to see how the parts relate, not as a parts reference or a procedure. Per the USPTO, the text and drawings of a patent are typically not subject to copyright; each patent here was checked for a copyright notice.

US Patent 6,523,294 — Revolver-safety lock mechanism

Brett Curry, Owen Patrick Cramer, Richard F. Mikuta, James M. Quill, Kevin R. Fleury · assigned to Smith & Wesson Corp. · filed 2001-04-12 · granted 2003-02-25. Full patent (USPTO)

The internal key-lock (lockarm and actuator) built into the frame of S&W revolvers, shown on a side view of a S&W revolver and in partial section at the hammer. Applies only to revolvers built with the internal lock.

Why this is the Smith & Wesson Model 642’s patent: listed on the maker’s patent-marking page — Virtual Patent Marking | Smith & Wesson — Smith & Wesson smith-wesson.com [4]: “6,523,294 All S&W® revolvers with internal locks”

Torque specifications

No sourced torque values from the manufacturer are recorded for this firearm. Where a fastener has a specified torque — action screws, scope bases, muzzle devices, barrel nuts — get it from the manufacturer or a gunsmith rather than estimating it.

What the manufacturer does say: The manufacturer's documents give no torque value. They say: "The barrel assembly is re-installed using the same tool and an accurate torque wrench." (Safety & Instruction Manual, Revolvers - Modern Style - J, K, L and N Frame (p/n 416560000, REV S&W_REVOLVER_112119), linked from smith-wesson.com revolver product pages, p. 26 (Gunsmith Advisory))

Materials and factory finish

As stated by Smith & Wesson. Prep, masking and cure depend on these; a polymer or aluminium part, a nitrided or anodised finish, and a blued steel part are each a different job. Variants with other finishes may exist — check the maker's page for the exact SKU on the bench.

Parts

No parts list from Smith & Wesson is transcribed for this firearm.

Smith & Wesson's own documents label the parts on these pages — the links open each document at the page:

• Model and features identification (labelled photo of the revolver): Smith & Wesson Revolvers (Modern Style) Safety & Instruction Manual — Smith & Wesson, p. 14 mcarbo.com [1]

Function check

• Verify every chamber is empty before each check.
• Cock the hammer slowly and confirm the cylinder locks up at each chamber before the hammer reaches full cock — this is carry-up.
• With the hammer at full cock, try to rotate the cylinder by hand. It should be locked, with only minimal play.
• Press the trigger in single action and confirm a clean hammer fall.
• Cycle the action in double action through every chamber and confirm the cylinder indexes and locks each time.
• Confirm the cylinder latches closed securely and the release frees it cleanly.
• Check that cylinder endshake is minimal and the cylinder gap looks even. If either seems off, see a gunsmith.

Maintenance

Lubrication points

• Yoke or crane barrel where the cylinder rides
• Ejector rod
• Hammer and trigger pivot pins (a single drop each)
• Cylinder stop

Cleaning notes

Lead and carbon build up on the front face of the cylinder and in the forcing cone, and left alone they eventually bind the cylinder. Clean the chambers thoroughly — a fouled chamber makes extraction difficult and is often mistaken for a timing problem. Keep lubrication sparing; revolver lockwork does not want to be wet.

Suggested inspection interval: roughly every 2000 rounds. This is a general guideline, not a manufacturer specification.

Wear parts to inspect

Hand · Cylinder stop · Ejector rod (confirm it has not unscrewed) · Forcing cone (inspect for cracks) · Yoke or crane alignment

Common issues

Also covers

The procedures above are reported to apply to: Model 442 · Model 638 and 649 (shrouded hammer variants). Verify against the manual for your specific model.

Similar manual of arms

• Smith & Wesson Model 10

Sourcing